1. Is it possible that "ATEC" is the battery charger that needs to be used with these batteries? It appears that the other battery case has a sticker on it. That sticker may have specs and charge details for those batteries.

That .pdf is very large, and could not see all of it, due to errors, but just wondering if that ATEC reference was for the charger, not the battery.

3. In the USA, batteries that are in cases (trays) like the ones on your batteries are in the Forklift or Traction category, are Flooded Lead Acid type, and would have charge voltages considerably higher than those listed in your post.

4. Also, perhaps the supplier of your batteries may have more data on the manufacturer and model number for your batteries.

I now found out, thanks to a member of the german photovoltaikforum.com, ATEC only deals with batteries and the buy what they get.I will have to look closer to the cells, if I can find some numbers or like that.

There are no more details on the Stickers on the tray; only the stickers you can see in the pictures

The supplier is a guy, who buys and sells used batteries, where he can get them ... not a professionall battery dealer

These are "5 EPzS 575" ... (I have just seen, I also was searching wrong in the net; OPzS are not EPzS)

In the upper part of this pdf, it states that Tab batteries have a target SG of about 1.290 when fully-charged, this, of course, is a Flooded Lead Acid battery. And, would imply that the Vabs would be 60 volts (for a 48 V nominal voltage), or a bit higher for absorb.

There may be some batteries in this series, that are Lead Calcium, which may need a somewhat lower Vabs.

that photo showing the battery bank has what looks like a plastic container of water in front of the bank. Doesn't that indicate these are flooded lead acid barreries?

@binkino, you should really know what you are buying before you pay for batteries.So far you have apparently paid for and taken delivery of a battery bank that you have no idea what the chemistry is, no idea what the charging parameters are, and it seems they are second hand and do you know hold old they are, nor do you have any idea who the manufacturer is or the battery model is.Have they been capacity tested and have they been rebuild or chemically treated in some way to 'restore' them and/or have they been power equalised.Do you see a problem here? I do.Your lack of understanding of battery charging and the terminology used, bulk, float, absorb is also of some concern.I am genuinely concerned that your lack of knowledge may be or could be dangerous, a 48volt battery bank can kill you, please get a professional installer to help youdgd(no offense intended)

the batteries are 'flooded' they are EPzS = PzS -> (see also the sticker on the trays)see also the Aquamatic hoses on top in the trays - and correct, the tank with dest. water

The cells I bought were directly delivered to the forklift-workshop-dealer, so he was able to check the cells / battery bank for me, before we put them to the basement in my house.He was very surprised, in what a good condition the cells are.I get them used, that is correct and I knew that before.They are build 09/2011 - so 5 3/4 years old.They should have about 90% SOH

I am sure you agree, if you don't use a knowledge repeatably, you forget. You remember, when you find this little tiny bit, that helps you to get back in.btw I am back in the charge states settings thing (the real problem is not the lack of knowledge, it is, why can't they use names, they can be translated in a clear word in other language... that would help a lot haha if it is not your natural language, you lose sometimes)

That is like with languages. In this case, English. If I don't use it a longer time, you 'forget' and have to use google translate or similar for some words. If you continue to use is, you get back in. That doesn't give "the big picture" If you read my posts, you also see how different my English skills differs from post to post.

I once was setting up the system and if it runs, you don't have to change settings anymore. You let it run. Since you buy new batteries or change some other things, they need adjust in the Classic.

NOW with the EPzS I will also have to think new, check the cells periodically, keep the settings in mind ...

Only information lack is the correct setting datas for the Classics.I know some basics about the chemistry (EPzS) and normally you can ask the manufacturer for the datas if you buy used cells, that is normally no problem. With ATEC I was wrong, okay that is right. But someone must have been making the cells and I will find out.ATEC is not a manufacturer, just ony a big seller, I now had found out, they buy and sell what ever they get...

But it was possible, someone knows "Atec batteries" and could help.And if the batteries would have been bad, I would have returned them to the seller. That was part of the deal.Tonight I also get some datas from a member of the german forum. I will test them now, if they work good with the cells.I also don't want to give them to high charging volts

Later I try to investigate the cells, also want to meassure the cells voltage and write them down, may be I find the real manufacturer. Some numbers and letters ...

But I understand your motives and warnings, thank you;)and what you can not know, I learned electrician and I don't do it like "ElectroBOOM" (YT) haha

Perhaps you should measure the Specific Gravity (electrolyte density) with your high quality Hydrometer, and record these readings in your new Battery Log Book.

Without knowing the manufacturer of these batteries and the exact charging specs for your batteries, you are operating in an unknown area.

Then measure the Resting battery voltage (no charge or discharge for 6 or more hours), and the electrolyte temperature.

While the person who delivered the batteries to you may know how to charge these batteries, the charge voltage and Float voltage seem very, very low to me, for this type of battery.

I am unfamiliar with the definition of EPzS, but believe it has roots in the German language.

In the USA, most Traction batteries are Flooded, high Capacity batteries, with AH Capacities rated at a 6, or 8 hour discharge Rate, and have a minimum SG of about 1.280, and some SGs range to as high as 1.320, or so. This range of SGs imply an Absorb voltage from a Solar type charger of 60.0 V, or higher, and a Float voltage of about 54 V, or a bit higher, at the rated reference Temperature (perhaps about 15 C in Eu, and 23 - 25 C in NA).

Almost all of the questions you raised in the first post will be derived from the specs from the battery manufacturer for your exact batteries.

You could search around the internet, looking for EPzS batteries from different manufacturers, looking for very similar looking batteries, as a starting point. The design and look of the watering system my also help you discover the manufacturer of the batteries.